Various hand held or portable lighting devices, including flashlights, are known in the art. Such lighting devices typically include one or more dry cell batteries having positive and negative electrodes. The batteries are arranged electrically in series or parallel in a battery compartment or housing. The battery compartment is also sometimes used to hold the lighting device, particularly in the case of flashlights. An electrical circuit is established from a battery electrode through conductive means which are electrically coupled with an electrode of a light source, such as a lamp bulb or a light emitting diode (“LED”). After passing through the light source, the electric circuit continues through a second electrode of the light source in electrical contact with conductive means, which in turn are in electrical contact with the other electrode of a battery. The circuit includes a switch to open or close the circuit. Actuation of the switch to close the electrical circuit enables current to pass through the lamp bulb, LED, or other light source—and through the filament, in the case of an incandescent lamp bulb—thereby generating light.
Flashlights and other portable lighting devices have conventionally employed a mechanical power switch in the main power circuit of the flashlight to turn “on” the flashlight and turn “off” the flashlight. When the user desired to turn “on” the flashlight, the user manipulated the mechanical power switch to mechanically connect two contacts to close the switch and complete the power circuit, thereby allowing current to flow from the positive terminal of the batteries, through the light source, and back to the negative terminal of the batteries. When the user desired to turn “off” the flashlight, the user manipulated the mechanical switch to disconnect the two contacts of the switch and thereby open the switch and break the power circuit. The mechanical switch in such devices, therefore, acts as a conductor in completing the power circuit and conducting current throughout the operation of the portable lighting device.
A variety of mechanical switch designs are known in the art, including, for example, push button switches, sliding switches, and rotating head switches. Such switches tend to be fairly intuitive and easy to operate by the user. However, portable lighting devices having just a simple mechanical power switch do not include automated operating modes, such as, for example, a blink mode, a power reduction mode, or an SOS mode. To include such automated functionality in a portable lighting device, the portable lighting device must have advanced electronics.
For example, multi-mode electronic flashlights and other portable lighting devices have been designed using an electronic power switch controlled by a processor of a microchip or microcontroller. In such lighting devices, the various modes that are programmed into the microchip are selected through the appropriate manipulation of a user interface, such as a momentary switch.
In one approach, the electronics of the multi-mode portable lighting device remain constantly connected to the power source. As a result, however, the electronics constantly consume power, thereby decreasing the useful battery life, or in the case of rechargeable batteries, the operational time between charges.
In another approach, a mechanical power switch, which is disposed electrically in series with the light source and controller, is used to simultaneously break the circuit powering the electronics and the light source. As a result, the electronics do not consume power from the batteries (or battery) when the portable lighting device is turned off. However, in order for the mechanical power switch to be used as the user interface to select different modes of operation by, for example, opening and then closing the mechanical power switch within a defined period of time, the microchip is provided with an alternative source of temporary power.
The alternative source of temporary power is provided so that when the mechanical power switch is opened the microchip will remain temporarily powered, even though the portable lighting device has been shut off, until the mechanical power switch is again closed. In the absence of the alternative source of temporary power, the microchip would lose power when the mechanical power switch is opened, causing the controller to reset and return to its default mode of operation the next time the mechanical power switch is closed instead of toggling to the next operational mode.
One or more capacitors arranged in parallel with the controller have been used as the alternative source of power. The capacitors are selected to have sufficient capacitance to power the controller for a suitable period of time, such as one to two seconds, following the opening of the mechanical power switch before falling below the reset voltage of the controller. Thus, as long as the mechanical power switch is again closed within the allotted time frame, the lighting device will begin to operate in the next mode of operation.
A disadvantage of this approach is that significant capacitance is required to be able to power the controller for an adequate period of time, resulting in increased cost. In addition, in some configurations, the required capacitor(s) may have a physical foot print that is larger than the amount of space available on the printed circuit board to be included in the portable lighting device.